In the metalworking industry of machine shops, a cutting tool is any tool that is employed to remove metal from the workpiece being machined. This removal is accomplished generally by means of a shear deformation. Essentially, with the workpiece or the tool in motion, the tool is placed in controlled contact with the workpiece to thereby remove material such as metal strategically, to thereby form the desired shape to the workpiece.
Tools generally employ a bit or insert, which is engaged to a holder. The bit or insert is formed of material sufficiently hard to cut the workpiece in the manner intended. Over time, the cutting formed by the bit or insert tends to dull from repeated contact with the workpiece to remove material. The insert must therefore be replaced to maintain the quality of the workpiece produced and the speed of the operation producing the parts formed by the fully machined workpiece. A dull tool insert will not only slow the process, it can easily yield inferior parts from chatter and other problems inherent to contact of a dull insert with the workpiece being machined.
Additionally, the cutting tool insert must employ a specific geometry so as to place the cutting edge of the tool insert in proper contact with the workpiece. Concurrently, the rest of the tool insert must be spaced from the workpiece to prevent dragging of non cutting surfaces upon workpiece. Other elements of tool insert geometry such as the angle of the cutting edge, the flute width, the tool margin and hardness of the cutting edge also must be maintained during use of the tool insert to work upon the workpiece.
Frequently employed in modern machining is the lathe, particularly a Computer Controlled (CNC) lathe. Such devices generally spin the workpiece against a plurality of sequentially positioned tool inserts to thereby yield a final component. One operation which can be employed with the lathe is the art of broaching. In broaching, instead of spinning the workpiece, the lathe's spindle is locked in place to hold the workpiece engaged in a fixed position. Thereafter a broaching tool insert is driven into and out of the workpiece being held by the spindle to thereby create keyways and slots within the workpiece.
This mode of operation of the lathe increases the number of operations which can be performed in a single chuck on a single lathe. Also, because the same machine is employed for two operations for a fixed in position workpiece, the accuracy of the dimensions of the final part formed by the fully machined workpiece is increased. This is because the workpiece need not be removed and remounted from machine to machine, which causes errors in the accuracy of sequential cuts to the workpiece. Shop labor time is also reduced since the workpiece need not be continually dismounted and remounted. Further, the need for specialized broaching machinery is reduced since the workpiece is held by the lathe for a plurality of cuts to the workpiece.
In the broaching operation, cutting tools are employed in a number of configurations. In one conventional configuration, carbide or similar tool inserts, have a cutting edge formed thereon which is a separate part that is brazed to a tool body portion. This creates a sturdy, yet permanently engaged cutting insert from the two individual parts. However, with only one cutting edge formed of two components, during each replacement of a dull tool insert, the set up must be re-registered to position the cutting edge of the tool insert to properly machine the workpiece.
A second configuration employs a tool insert which is replaceable and held in removable engagement with a tool body. This allows for replacement of the tool insert, when dull, by dismounting it from its holder, and engaging a new tool insert. However, the temporary engagement with the holder using screws or other means of engagement suffers from chatter during machining of the workpiece due to the minimal contact of set screws and the like with the tool insert to engage it to the holder. Additionally, such tool inserts generally require a new setup of the tool insert geometry each time the cutting tool insert is replaced.
Both conventional types of broaching tool configurations suffer from dulling of the single cutting edge of the cutting tool insert. Since they thus require frequent replacements machining time is significantly increased by the need to re-register the geometry of the cutting tool insert with the workpiece after each replacement. Accuracy of the parts formed by the machined workpiece suffers due to the numerous reconfigurations of the tool insert each time the single cutting edge wears past desired specifications.
During replacement of brazed cutting tool inserts the dismounting of the cutting tool insert and subsequent brazing of a new cutting edge portion to the body, is tedious at best. The process then requires the entire cutting tool insert to be registered in engagement relative to the machine and the workpiece position to yield the desired material cuts to the workpiece.
Replacement of an insertable and screw-held cutting tool inserts, while somewhat easier, still suffer from chatter and other problems due to the nature of the engagement of the cutting tool insert to the body of the tool holding it. Further, due to the variance in dimensions of each different cutting tool insert, re-registration of the geometry of the insert to the workpiece is virtually assured.
Accordingly, there exists an unmet need for a method for a broaching cutting tool device which provides the convenience of a replaceable cutting tool insert with a tool body. Such a device should however be free of the problems inherent with conventional tool inserts of chatter due to poor engagement with the holder, and the need to re-setup the tool geometry each time, due to varying engagement with the body holding it.
With respect to the above, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components or steps set forth in the following description or illustrated in the drawings. The various apparatus and methods of the invention are capable of other embodiments and of being practiced and carried out in various ways which will be obvious to those skilled in the art once they review this disclosure. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based, wherein a cutting tool insert is shaped to engage with the cutting tool body holding it, in a manner to yield a stronger and more accurate mount, may readily be utilized as a basis for designing of other devices, and methods and systems for carrying out the several purposes of the present disclosed device and method. It is important, therefore, that the objects and claims be regarded as including such equivalent construction and methodology, insofar as they do not depart from the spirit and scope of the present cutting tool invention.